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Skeletal Muscle Flashcards

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1
Q

Sarcolemma

A

Cell membrane of a muscle fiber

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2
Q

Sarcoplasm

A

Cytoplasm of a muscle cell

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3
Q

Myofibril

A

Highly organized bundles of contractile and elastic proteins that carry out the work of contraction

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4
Q

Sarcoplasmic Reticulum

A

A form of modified ER that wraps around each myofibril like a piece of lace. It concentrates and sequesters calcium ions with help of calcium ATPase

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5
Q

Transverse tubules

A

Aka t-tubules. Extensions of the cell membrane that associate with the ends of the SR

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6
Q

Ends of SR are called

A

Terminal cisternae

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7
Q

Thin filaments

A

Made up of microfilament actin (protein) which makes up muscle fiber, one actin is globular protein. Multiple G actin molecules polymerize to form long chains or filaments.
The “rope”

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8
Q

Thick filaments

A

Made from motor protein called myosin (2 polypeptide tail, hinged heads. Ability to create movement.
Arranged so that the myosin heads are clustered at end of the filament and the central region of the filament is a bundle of myosin tails
Attached to M line
“ hands on rope”

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9
Q

What is sarcomere

A
  • The contractile unit of myofibril.
  • Consists of a repeat pattern of light and dark bands which are thick and thin filaments
  • Contains 2 Z disks, I band, A band, H zone and M line
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10
Q

A band

A
  • Anisotropic band because It’s scatters light unevenly
  • Darkest band, encompasses entire length of thick filament
  • On the outer edges of the a band contains thick and thin filaments overlapping
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11
Q

H zone

A

Central region of the a band is lighter than the outer edges of theA band because the H zone is occupied by thick filaments only
• Tails of thick filaments contained here

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12
Q

M Line

A

The middle of the sarcomere attachment site for the thick filaments

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13
Q

Z disks

A

Attachment site of Actin and the ends of one sarcomere

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14
Q

I band

A

Lightest band found adjacent to each Z disk, represent a portion of the sarcomere that has just thin filaments

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15
Q

What is the role of troponin

A

It regulates the on and off positioning of tropomyosin

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16
Q

What is the role of TROPOMYOSIN

A

It allows for the “off” relaxed and “on” contracted states of sarcomere

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17
Q

How does troponin regulate contraction

A

When calcium levels increase in cytosol, Calcium binds to TN, This pulls tropomyosin away from Actin’s myosin binding site.
When calcium concentrations decrease, Calcium unbinds from troponin, allowing tropomyosin to cover actin’s myosin binding sites

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18
Q

Which receptor are involved in the initiation of contraction and where are they located

A

Nicotinic Cholinergic receptors

On the motor and plate

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19
Q

Receptors on the motor end plate combine with what neurotransmitter

A

ACh

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20
Q

After ACh combines with receptor at the motor and plate which channels open

A

Sodium and potassium Channels open

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21
Q

What net ion change takes place in order to depolarizes the cell to initiate contraction?
What does this create

A

Na+ entry

End plate potential

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22
Q

EPP is the same as what and where does it spread to

A

An action potential

Across sarcolemma into t- tubules

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23
Q

What receptor is located in the T tubules

A

DHP (dihydropyridine) receptors

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24
Q

What kind of receptor is DHP and once activated what do they do

A

Voltage sensitive

Open Ca channels on SR

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25
How does a muscle fiber end contraction
Calcium must be removed from the cytosol. | The SR pumps calcium ions back into its lumen using a calcium ATPase
26
How much ATP does aerobic metabolism create with one glucose
30
27
How much ATP does anaerobic metabolism yield for one glucose
Two ATP
28
What is muscle fatigue
The inability to sustain a contraction even when signaled
29
What are 4 factors that are believed to contribute to muscle fatigue
Lack of ACH Glycogen depletion Reduction in calcium release Increased Pi production of CaPO4 Loss of K++
30
Why do H+ and in organic phosphate accumulate during exercise
H+ accumulat as a result of ATP hydrolysis | Pi accumulates when ATP and phosphocreatine are used for energy in muscle fiber
31
What is the role of myoglobin in skeletal muscle
It has a high affinity for oxygen this allows it to act as a transfer molecule bringing oxygen more rapidly to the interior of fibers
32
Which fiber type has a most MYOGLOBIN
Oxidative fibers have the most because they rely on oxidative phosphorylation for ATP ( type I and type IIA)
33
What is the role of creatine phosphate (phosphocreatine)in muscle
It is a backup energy source for muscle. it is high energy phosphate bonds are created from creatine and ATP at rest. Anaerobic
34
How can muscles become condition to be more fatigued resistance
Muscle fibers have plasticity and can shift their type depending on their activity. Fast twitch type to a muscle fibers are glycolytic but become more oxidative with endurance training. Endurance training increases capillaries and mitochondria in muscle cells. The more oxidative the muscle type the less fatigue resistant.
35
What is asynchronous recruitment
This is a sustained contraction used by the nervous system to avoid fatigue. It's the alternation of active motor units where some motor units rest between contractions preventing fatigue.
36
Why do long and short sarcomere develop less tension the sacromere at optimal length
Long sacromere barely overlap & form few cross bridges and don't generate much force Short sarcomere overlap too much at the beginning, they move a short distance, this prevents cross bridge formation andd dereased tension Optimal Is when the sarcomere are slightly overlapped-->numerous cross bridges between thick and thin filaments
37
What is the relationship between tension and cross bridges
The amount if ension is directly proportional to the amount of cross bridges formed between thick and thin filaments
38
What is temporal summation in muscle fiber
If the interval of time between action potentials is shortened then the muscle fiber does not have enough time to relax completely between both stimuli, this results in a more forceful contraction
39
What is a motor unit
This consists of a somatic motor neuron and the group of muscle fibers that function together controlled by this neuron
40
Muscles responsible for fine movements will have more or fewer muscle fibers in its motor units
Fewer
41
Are the types of muscle fibers in a single motor unit the same or different fiber types
Same
42
What is motor unit recruitment and how does it take place
It is the force of contraction and skeletal muscle increase by recruiting additional motor units. And weak stimulus activates neurons with low threshold. As stimulus increases additional motor neurons with higher thresholds are activated
43
Single unit smooth muscle
The cells are electrically connected by gap junctions and they contract as a coordinated unit
44
Multi unit smooth muscle
The cells are not linked electrically and each muscle cell functions independently
45
How are the arrangement of contractile fibers in smooth muscle different from those in skeletal muscle
Smooth muscle contractile fibers are not arranged in sacromeres and they lack the distinct banding patterns of striated muscle.
46
What type of summation is motor unit recruitment in smooth muscle
Temporal summation, Like that of neurons and graded potential
47
Explain the events of excitation contraction coupling in and smooth muscle
1. No action potential 2. Signal is sent from autonomic motor neuron 3. This activates an increase in calcium in cytosol from ECF and SR 4. Calcium binds to CALMODULIN 5. This activates the enzyme MLCK, This phosphorylates myosin light protein chains and increase myosin ATP ase activity 6. Active myosin cross bridges slide along actin and create muscle tension
48
What is the role of MLCK/MLCP ratio in smooth muscle contraction
Less contraction = MLCP dominates MLCK, Ca++ is desensitized, decreasing myosin ATPase activity More contraction = signal molecules decreased MLCP activity, MLCK dominates, Ca++ more sensitive
49
What are the 2 sources of calcium in the smooth muscle
SR and ECF
50
How do calcium levels and smooth muscle cell become elevated
1. Voltage gated calcium channels open in response to depolarization 2. Ligand gated calcium channels also known as receptor operated calcium channels (ROCC) 3. Stretch activated channels 4. SR-->RYR -->calcium induced calcium release (CICR) or IP3-->SR 5. When SR Ca depleted, ST1M1 sends msg to cell membrane to allow more Ca into cell
51
How is smooth muscle relaxation different from skeletal muscle relaxation
Smooth muscle can stay contracted and it doesn't fatigue, it consumes minimal ATP
52
The membrane of the t-Tubules contains receptor that are sensitive to
Voltage
53
Multiple globular molecules polymerize to form long chains or filaments
Actin
54
What connects thick filaments to thin filaments that span the space between myosin and actin molecules
Cross bridges
55
Straighted muscles are so called because of the repeating pattern of light and dark bands. One repeating unit of the banding pattern is called a
Sarcomere
56
The tension generated in a skeletal muscle fiber is directly proportional to the number of
Active cross bridges formed
57
Each myosin head has a binding site for
Actin and ATP
58
The hydrolysis of ATP causes myosin to immediately
Rotate into a position cocked to bind to actin
59
The binding of ACh to its receptor at the neuromuscular Junction causes the opening of a
Channel for both sodium and potassium
60
The relaxation of skeletal muscle relies on the activity of what which decreases cytoplasmic calcium concentration
CaATPase
61
Within a single fiber the tension developed during a twitch depends upon the
Length of the sarcomere prior to contraction
62
A motor unit consists of
One neuron and all the skeletal muscle fibers it controls
63
Which fibers generate more force
Fast twitch fibers
64
Which fibers fatigue sooner
Fast twitch fibers
65
The nervous system avoids muscle fatigue during submaximal contraction by
Asynchronous recruitment
66
Smooth muscle cells do not have which proteins
Troponin
67
Which is not a property of single unit smooth muscles A. Smooth muscle cells are connected by gap junctions B. Their contraction occurs in a coordinated manner C. Electrical responses travel directly between cells D. Only some of this smooth muscle cells are associated with autonomic neuron axon terminals E. Each cell functions independently of its neighbor
D.. Only some of this smooth muscle cells are associated with autonomic neuron axon terminals
68
What are comparisons of cardiac monocytes to other muscle cell types
1. Like smooth muscle cells some cardiac cells have peacemaker potentials 2. Like some smooth muscle cells cardiac cells are electrically coupled 3. Like skeletal muscle cells actin and myosin are organized into sarcomere 4. Like smooth muscle cells cardiac muscles are under hormonal control
69
What is Titan
A very large protein that is positioned at the ends of the thick filaments and extend to the Z disks. It is a Spring like protein that coils up with contraction and then recoils to push the Z disks apart with relaxation

Physiology (9 decks)

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